I've posted about my experience before, but I'll post it here again. I get a lot of PMs about it (I'm terrible at remembering to reply to PMs, for that I apologize!!), so hopefully this will answer many questions about it.
We didn't have an internship program established with Chicago Express when I applied; I was doing it on my own. I just sent my resume, visited the General Offices, kept in touch with the recruiters, and so on. I was very interested in doing in the internship, and even more interested in working for the company some day. I made sure they knew that. I don't really know the requirements for our internship program... I figure I met them. I believe a 2.5-2.8 GPA is required, as well as a Commercial Certificate, and being enrolled in an aviation degree program that provides college credits for the experience. However, you can do the internship the semester immediately after graduation.
When I applied, the internship was less competitive. I was actually the only intern that year... normally they had 3. But I guess the others who had been selected turned down the offer for various reasons. Now, the internship is highly competitive. There were many applicants this past year, and 2 were selected. (I think 15 to 20 or so applied? That's quite a bit.) Like I said, I don't know all the selection criteria, but I believe personality and drive plays a large part in who they select. We are a small company, so they base their selection on who will fit in here, and will work hard during the internship. You really have to want to work here, and make that known.
Now, there are two interviews involved in selection from what I understand. Phone interviews with the HR recruiter and the VP of Operations.
When I interned, I worked in every part of the operation. I worked on projects for the VP of Operations, VP of Customer Service, Director of Inflight, Director of Tech Pubs (a lot of work there), Director of Training, Chief Pilot, Dispatch, Training Department, just to name a few. I had a desk set aside for me in the Tech Pubs office, and did a lot of work in the offices with all the management personnel.
I also did a lot of "aircraft stocking" which meant sitting at our ramp, and getting in the aircraft to revise the Aircraft Flight Manual, checklists, takeoff tables, etc. I'd just spend most of the day hanging at the ramp in Operations running out to planes as they came in to update on-board items. Same is done with current interns.
Although unpaid, I think the greatest benefit of working as an intern was the ability to jumpseat. I used that benefit quite a bit, jumpseating something like 80 hours in the Saab. By the time I left, I had a great understanding about procedures, limitations, systems, etc. of that airplane. Helped me a lot when I got to training, although many of the procedures changed. I had collected a lot of materials on the Saab during the internship to help me out as well, like systems manuals, maintenance training manuals, etc.
I think there are huge benefits to doing a regional internship. I wish I would have done one at a major as well (applied to Southwest, but was too close to graduation). You will learn a LOT about the airlines working on the front lines. I wouldn't trade that experience for anything. Plus, I was very lucky to be asked to return as a pilot after graduation to that same company.
Hope that answers some of your questions. If you have more, ask them on here, I'm sure many on here could benefit from them.